If what you mean by 5.1 is SACD/DVD-A through what some AVRs call "ext in" then (again) some AVRs can do bass management for the sub. The Denon series from 38xx up do this on the "input menu" (for some odd reason, you'd think it would be on the speaker menu
). I note that it has no effect on 2.1 (duh) but for some reason when I use Dolby PLII-x for music it also seems to apply... can't figure that one out. So I would check your AVR and see if you can adjust the (equivalent of) "ext in" sub level. You may get lucky.
